1. Field of the Invention
The present invention generally relates to a projection picture display apparatus such as, for example, a projection-type television receiver set and, more particularly, to a remote control system used in the projection picture display apparatus. Still more particularly, the present invention relates to the arrangement of an optical command sensor of the remote control system in the projection picture display apparatus.
2. Description of the Prior Art
Television receiver sets now available in the commercial market, including those of projection type, have a remote control system comprising a hand-held remote controller, or optical command emitter, for generating an infrared beam of a particular characteristic descriptive of a particular command such as, for example, a channel selection command, an audio sound adjusting command or a power on-off command, and a command sensor or receiver operable in response to the infrared beam to operate a circuit component assigned to accomplish such particular command. One example of the prior art back-projection television receiver sets is illustrated in FIGS. 1(a) and 1(b) in schematic front elevational and side sectional representations, respectively.
As shown in FIGS. 1(a) and 1(b), the back-projection television receiver set comprises a cabinet C having top and bottom walls, front and rear walls and a pair of opposite side walls all assembled to render the cabinet C to represent a generally rectangular box-like configuration. The cabinet C has upper and lower compartments defined therein. A video projector unit P is housed within the lower compartment of the cabinet C and comprises three cathode ray tube units each including a red, green or blue color cathode ray tube 1 and a projector lens assembly 2, said video projector unit P being so supported and so positioned that a picture reproduced by the cathode ray tube 1 can be projected by the projector lens assembly 2 towards a back-projection screen 4, supported in the front wall of the cabinet C, after having been reflected by a reflector mirror 3 supported in the rear wall of the cabinet C. The projector lens assembly 2 serves not only to relay the television picture to a remote place, that is, onto the back-projection screen 4, but also to enlarge the picture being projected onto the back-projection screen 4. The front wall of the cabinet C has at a location immediately below the back-projection screen 4 a utility panel where various adjustment knobs are installed for the access of a viewer thereto. The utility panel includes a sensor window defined in alignment with the infrared command sensor 5 for receiving the infrared command therethrough.
Since, as hereinabove discussed, the command sensor in the prior art television receiver set of back-projection type is installed in the utility panel immediately beneath the back-projection screen so that the infrared command emitted from the hand-held remote controller (not shown) can be received through the sensor window, it often occurs that a major portion of the infrared rays of light representing the infrared command emitted from the remote controller will not be effectively received by the command sensor, thereby posing a problem associated with the directionality and the distance of reach of the infrared command.
In other words, since the infrared rays of light emitted from the remote controller are scattered even though the remote controller is carefully aimed at the command sensor spaced a substantial distance from the remote controller, the intensity of the infrared rays of light received by the command sensor is appreciably reduced. Moreover, the coverage of the command sensor, within which the command sensor can respond to the infrared command, is relatively narrow. Because of these reasons, aiming the remote controller at the command sensor as accurately as possible is not easy, and this is particularly true where a substantial distance between the remote controller and the command sensor is realized. These problems are not uncommon in a back-projection television receiver set having a relatively large screen.
In addition, the provision of the sensor window at the utility panel immediately beneath the back-projection screen brings about a problem associated with the aesthetic layout of the cabinet.
The Japanese Laid-open Utility Model Publication No. 62-8761, published January 20, 1987, discloses a back-projection television receiver set wherein first and second reflector mirrors are disposed between the video projector unit and the back-projection screen, the first reflector mirror being housed within the lower compartment of the cabinet and the second reflector mirror within the upper compartment of the cabinet in opposition to the back-projection screen. The command sensor is installed, in one embodiment, within the upper compartment and immediately below the second reflector mirror so that the infrared beam emitted from the external remote controller can be received after having passed through the back-projection screen. In another embodiment of the Japanese publication referred to above, the command sensor is installed within the lower compartment immediately above the video projector unit so that the infrared beams emitted from the external remote controller can be received after having passed through the back-projection screen and then reflected by the second reflector mirror.
In any event, although the Japanese publication referred to above discloses the command sensor installed completely within the cabinet with no sensor window defined at the utility panel, this is solely for substantially eliminating the problem associated with the aesthetic layout of the cabinet as a whole. No special consideration has been paid whatsoever in connection with the position of the command sensor in relation to both of the nature of the back-projection screen and the infrared rays of light emitted from the remote controller and, therefore, the Japanese publication explicitly suggests the positioning of the command sensor at any suitable location within the cabinet if and only if the command sensor so positioned can receive the infrared command either directly or reflected from one or both of the reflector mirrors. Accordingly, the remote control system disclosed in the Japanese publication referred to above has a problem associated with the directionality of the remote controller.